ADR is a noxious and unintended response to a medicinal product related to any dose. A causal relationship between the medicinal product and the adverse response is at least a reasonable possibility.

Lack of efficacy is if the participant had poor seizure control (defined as experiencing a seizure despite being on the maximum dose for equal to 2 weeks). The participant can withdraw at any time due to lack of efficacy.

Change from baseline in the number of concomitant AEDs along with the Perampanel will be reported.

A 50% or 75% responder rate is percentage of participants who experience at least 50% or 75% reduction in all seizure frequency during the study.

A 50% or 75% responder rate for SGTCS is percentage of participants who experience at least 50% or 75% reduction of SGTCS frequency during the study. Focal to bilateral toni-clonic seizures (FBTCS) replaces older term SGTCS. FBTCS is a seizure type with focal onset, with awareness or impaired awareness, either motor or nonmotor, progressing to bilateral tonic-clonic activity.

Participants will be considered seizure-free if participants will not experience any partial-onset seizure during the study.

Seizure frequency is based on the number of seizures per 28 days, calculated as the number of seizures over the entire time interval divided by the number of days in the interval and multiplied by 28.

SGTCS frequency is based on the number of SGTC seizures per 28 days, calculated as the number of SGTC seizures over the entire time interval divided by the number of days in the interval and multiplied by 28. FBTCS replaces older term SGTCS. FBTCS is a seizure type with focal onset, with awareness or impaired awareness, either motor or nonmotor, progressing to bilateral tonic-clonic activity.

The Italian version of the QOLIE-31 will be used in this study. The QOLIE-31 inventory is a 31-item self-administered questionnaire evaluating Quality of Life (QOL) perception in adults 18 years or older with epilepsy in 7 domains: seizure worry, emotional wellbeing, energy/fatigue, cognitive functioning, medication effects, social functioning, overall QOL. The overall score is derived by weighing and then summing the 7 domain scores. Pre-coded numeric values for some domains are such that a higher number reflects a more favorable health state; others are such that a higher number reflects a less favorable state. Pre-coded values are converted to 0 to 100 point scores; a higher converted score indicates a higher self-reported QOL.

The ESS is a self-administered questionnaire with 8 questions. It provides a measure of a participant's general level of daytime sleepiness, or average sleep propensity in daily life. The ESS asks the participant to rate, on a 4-point scale (0 [low] to 3 [high]) his or her usual chances of dozing off or falling asleep in 8 different situations or activities that most people engage in as part of their daily lives. The total ESS score provides an estimate of a general characteristic of each person's average level of sleepiness in daily life (0= no chance of dozing/no daytime sleepiness to 24=high chance of dozing/lots of daytime sleepiness).

I-Epi is a questionnaire specific for the assessment of irritability in adult participants with epilepsy. I-Epi is an 18-item self-administered questionnaire based on four dimensions related to irritability in participants affected by epilepsy (physical functioning, verbal functioning, temperamental functioning, and epilepsy functioning). Participants have to rate their irritability level on a 6-point Likert scale where 1="never," 2="almost never," 3="rarely,"4="sometimes," 5="often," and 6="always". Higher score means more irritability.

Predictive factors include age, age greater than or equal to (>=) 60 years, age less than (<) 18 years, gender, body mass index (BMI), age at seizure onset, age at diagnosis of epilepsy, time since diagnosis of epilepsy, baseline 28-day seizure frequency, seizure type, epilepsy familiarity (yes or no), epilepsy surgery (yes or no), focal known etiology (yes or unknown), number of seizures at baseline, number of AEDs at baseline, presence or absence of enzyme-inducing AEDs, eziologia vascolare (yes versus other). Regression coefficient will be determined to characterize the association between predictive factors and response to perampanel.